Abstract [en]

This report illustrates the making of a wooden propeller for a Champion 7 EC, a single-engined sportsplane. The purpose is to replace a metalpropeller in order to lower maintenance costs. This project contains calculating values, manufacturing one or more prototypes in order to check values and if necessary; change values, and in the end manufacturing a propeller which is approved for flight.
We started with calculating values on pitch, chord, length etc. based upon data on the engine of a Champion 7 EC and of the original metalpropeller. The material is birchwood and epoxy approved for flight. Before manufacturing the propeller one has to make pressure tests of the birchwood and make adhesive tests. If the material passes the tolerances the manufacturing can begin.
The propeller is made in following steps: first one has to calculate values on diameter, pitch, blade angles, chord and the thickness of the blade. Based upon those values paper templates is made of the blade profiles and blade forms. The wood is cut into right shape and glued together to form laminates which in turn are glued together into a propellershape. The propeller is then sawed, hoed, filed and grinned into right shape and size with great precision.
The result of this project is finished calculations, paper templates and two prototypes. We had no time to make a propeller approved for flight but we’re still pleased with the result since the most important part of the project is to calculate accurate values that can be used to make more propellers in case the first one has to be replaced.